Reddit in particular has very little besides it's massive numbers to actually keep users on their platform. I don't use Twitter or Facebook anymore, but at least with those platforms there would be specific celebrity accounts or friends and family that would provide a reason to stay.
Because reddit was so focused on anonymity, you didn't need the "celebrity" accounts to move platforms to make the alternatives feel viable. Even with just a small portion of users moving here it feels completely natural.
I tried Squabbles and got so confused. Took me forever to realize that the post was on the left column and the replies were on the right column. I stupidly thought Squabbles was combining Twitter and Reddit and thought the two columns were completely independent from one another. It makes sense to me now, but my simple brain likes this layout.